The Origin of Species by Means of Natural Selection, Or, The Preservation of Favored Races in the Struggle for Life

adapted admit affinities allied species analogous ancient appear beak become bees believe belonging birds breeds cause cells characters cirripedes classification climate closely allied color common progenitor continent crossed crustaceans degree developed difficulty distinct species disuse divergence domestic doubt eggs embryo Embryology existing extinct extremely facts favorable female fertility flowers formations forms fossil Fritz Müller Gärtner genera genus geological given Glacial period gradations greater number habits Hence hybrids hybrids produced important individuals inhabitants inherited insects instance instincts intercrossed jaws larvae less living male mammals manner Marsupials migration modified descendants natural selection naturalists nearly nest occasionally offspring Palaeozoic parent parent-species peculiar perfect pigeon pistil pollen present principle probably produced quadrupeds ranked reciprocal crosses remarked reproductive resemblance rudimentary organs seeds Silurian slight South America stage stamens sterility structure successive suppose tend tion variability variations vary whilst whole widely different wings young